Passive hybrid systems for earthquake protection of cable-stayed bridge

The performance of passive hybrid control systems for the earthquake protection of a cable-stayed bridge under real earthquake ground motion is presented. A simplified lumped mass finite-element model of the Quincy Bay-view Bridge at Illinois is used for the investigation. A viscous fluid damper (VFD) is used as a passive supplemental energy dissipation device in association with elastomeric and sliding isolation systems to form a passive hybrid control system. The effects of non-linear viscous damping of the VFD on the seismic response of an isolated cable-stayed bridge are examined by taking different values of velocity exponent of the damper. Further, the influence of a variation in viscous damping on the response of the isolated bridge is also investigated. The seismic response of the bridge with passive hybrid systems is compared with the corresponding response of the bridge with only isolation systems, as well as with the uncontrolled bridge. The results of the investigation show that the addition of supplemental damping in the form of a viscous fluid damper significantly reduces the earthquake response of an isolated cable-stayed bridge. The non-linear viscous damping is found to be more effective in controlling the peak isolator displacement of the isolated bridge while simultaneously limiting the base shear in towers.